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ANSC 311 - Metabolic Physiology > Lecture 2 - Digestion and Absorption > Flashcards

Lecture 2 - Digestion and Absorption Flashcards

1
Q

Digestion

A

the process by which foodstuffs are broken down by the GIT into absorbable units

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2
Q

4 types of digestion processes

A
  1. mechanical
  2. chemical
  3. enzymatic
  4. microbial
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3
Q

Mechanical digestion

A
  • mastication (chewing)
  • grinding of gizzard (birds)
  • movement of GIT (segmentation and peristalsis)
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4
Q

Chemical digestion

A
  • gastric acid (HCl; pH = 1.5-3.5)
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5
Q

Absorption

A

the process of moving digested products through the gut mucosal wall (transcellular or paracellular)

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6
Q

3 types of absorption transport mechanisms

A
  1. passive transport (transcellular or paracellular
  2. osmosis
  3. active transport (primary and secondary)
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7
Q

What is the amount of water secreted dependent on?

A
  • diet; carnivore vs herbivore
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8
Q

What is the location of water absorption dependent on?

A
  • the species
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9
Q

In what form are carbohydrates transported across cell membranes

A

MONOSACCHARIDES
- glucose
- fructose
- galactose

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10
Q

What are the 3 disaccharides?

A
  1. sucrose = gluctose + fructose
  2. maltose = gluctose + gluctose
  3. lactose = gluctose + galactose
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11
Q

What are 2 polysaccharides consumed in a diet?

A
  1. starch
  2. cellulose
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12
Q

Dextrins

A

mixtures of polymers of glucose units linked by alpha-1,4 or alpha-1,6 glycosidic bonds

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13
Q

What polysaccharide can amylase not digest? Why?

A
  • cellulose
  • cannot digest the beta-1,4 glycosidic bond but microbes can
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14
Q

What are the steps of CHO digestion?

A
  1. Mouth: starch, lactose, sucrose, and cellulose enter; alpha-amylase in mouth from saliva; end up with starch dextrins, isomaltose, maltose, lactose, sucrose, and cellulose
  2. Stomach: low pH stops action of amylase
  3. Pancreas: action of pancreatic alpha-amylase = isomaltose, maltose, lactose, sucrose, and dextrins
  4. Mucosal cell membrane-bound enzymes (oligoglucosidase, maltase, lactase, sucrase): end up with glucose, fructose, and galactose which enter the portal circulation and are taken to the liver
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15
Q

During what 2 points of CHO digestion is alpha amylase secreted?

A
  1. saliva
  2. pancreas
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16
Q

How are monosaccharides absorbed?

A
  • secondary active transport
  • 3 transporters = SGLT1, GLUT5, GLUT2
17
Q

What breaks down starch?

A

amylase (salivary and pancreatic)

18
Q

4 structures of amino acids

A
  1. primary = aa chain
  2. secondary = folding; hydrogen bonding of peptide backbone
  3. tertiary = packing; side chain interactions forming 3D structure
  4. quaternary = interaction of more than 1 aa chain
19
Q

What form are 90% of ingested fats in?

A
  • triglycerides
20
Q

Where are bile acids produced?

A
  • produced by liver, stored by gallbladder to digest fat
21
Q

Are bile acids fat soluble?

A
  • no, they stay in the gut working until actively transported in the ileum
22
Q

What is the mechanism of ‘attack’ for bile acids?

A
  1. bile salts coat fat droplets
  2. pancreatic lipase and colipase break down fats into monoglycerides and FA stored in micelles
    3 a. monoglycerides and FAs move out of micelles and enter cells via diffusion
    3 b. cholesterol is transported into cells by membrane transporter
  3. absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons
  4. chylomicrons released into lymphatic system
23
Q

What is a chylomicron composed of?

A
  • triglyceride + cholesterol + protein
  • formed in intestinal cells after fat absorption
24
Q

Purines and pyrimidines

A
  • purines: adenine, guanine
  • pyrimidines: thymine, cytosine, uracil
25
Q

Chromosome structure

A
  • strands of DNA wrap around a protein (histone) forming nucleosomes
  • nucleosomes coil together forming chromatin
  • chromatin loops and coils together forming supercoils
  • supercoils bunch together = CHROMOSOME
26
Q

How are nucleic acids digested and absorbed?

A
  1. denatured by gastric acid
  2. broken down to nucleotides by pancreatic nucleases
  3. phosphatase on brush border cleaves phosphate ion
  4. nucleosidase catalyzes breaking of covalent bond btw nitrogenous base and pentose sugar
27
Q

Where are nucleotide breakdown products absorbed?

A
  • duodenum and jejunum via active and secondary active transport

ANSC 311 - Metabolic Physiology (17 decks)

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